Comparative Analysis for an Electric Power Steering System

This paper presents a comparative analysis of three different motor structures designed for an electric power steering system (EPS) used in automotive industry. For automotive applications, high torque and power density, low torque ripple and wide speed range are needed. In order to make the comparison as transparent as possible, at first, the existing Interior Permanent Magnet Synchronous Motor (IPMSM) has been modeled by means of Finite Element Method (FEM) so as to check the electromagnetic behavior, (i.e. flux density, cogging and electromagnetic torque) weight and costs of active materials. In fact, the specifications for the new designed motors coincide with the characteristics of the IPMSM mentioned above (mounted on an actual EPS unit). Next step was the design, optimization and modelling of the two new machines i.e. one PMSM with a different rotor structure regarding the magnets shape (V-shape design) and finally a synchronous reluctance machine (SynRM). Moreover, real-time model in the loop (RTMiL) programs are created to simulate transient behavior of the machines.